This invention relates to a dispenser and/or diluter and, more particularly, to a hand-held dispenser which can repeatably deliver a precise quantity of liquid and which can also repeatably collect a precise quantity of a first liquid and then deliver the first liquid diluted with a predetermined amount of a second liquid.
There have been previously devised various types of apparatus for repeatably delivering a precise amount of liquid. Many types of hand-held syringes are capable of this task. However, in most cases it is necessary to refill the syringe after each use or to provide a number of different "stop" positions for the syringe plunger. This latter technique requires special operator control and generally yields only a very limited number of samples for each full stroke of the piston.
Responsive to the need for a repeatable liquid delivery system having the capacity for delivering large numbers of samples without refilling, there have been devised various types of plunger bottle dispensers, examples being disclosed in U.S. Pat. Nos. 3,191,807, 3,430,813, 3,730,398 and 3,741,444. Typically, these units comprise a plunger and a first check valve which allows liquid to pass into a chamber when the plunger is released. A second check valve allows the liquid to be delivered when the plunger is depressed, and a relatively large capacity bottle serves as the source from which liquid is drawn in through the first check valve. This type of bottle dispenser system is found to operate satisfactorily in some applications, but there is a degree of inconvenience associated with the size and bulk of the bottle and the frequent necessity of bringing test tubes or vessels to the vicinity where the bottle is located. It is one object of the invention to provide solutions to these prior art problems as set forth.
Previous techniques have also been devised for repeatably diluting a precise quantity of a first liquid in a predetermined quantity of a diluent liquid. Unfortunately, most of these techniques require relatively complex equipment and/or operations wherein the liquids are separately loaded from different sources or where a relatively bulky equipment is provided with bottle-type sources. Again, single-shot diluters are known, as well as those types wherein an operator is required to manipulate a plunger to different "stop" positions to obtain a desired result. This requires operator dexterity and is subject to human error. Also, those systems which are in the form of hand-held syringes require constant reloading of both types of liquids and are not capable of delivering even moderate numbers of diluted samples without such reloading. It is a second object of the present invention to provide solution to these further prior are problems as set forth.